Vegetable oils and animal fats, but other lipid phases, contain a variable proportion of accompanying substances (also called gums or concomitant substances) that must be removed to achieve quality requirements for the use of these oils, fats, and other lipid phases. These impurities are mostly at least partially hydrophilic and result in the formation of an emulsion upon contact with water. Examples of these accompanying substances are phospholipids, glycolipids, free fatty acids or polyphenols. While phospholipids have a high water binding capacity, this is true only to a small extent for free fatty acids. However, it is known that in the presence of a mixture of these accompanying substances in an oil, very stable emulsions occur when water is mixed into the oil. This leads to a situation where the resulting emulsion can no longer be separated by physical measures. Further, it is known from the prior art that the stability of such an emulsion increases with increasing water content. For the removal of these accompanying substances in an oil, aqueous extraction processes are known from the prior art in which, for the abovementioned reasons, removal of the accompanying substances is performed by adding the lowest possible volume of water. In WO 1994/021762 A1 (Removal of Phospholipids from Glyceride Oil), a degumming process is presented, in which first citric acid at a concentration of 50% by weight using a mixing ratio of 0.1 to 0.4% by weight is mixed with the oil to be purified. After a reaction time 0.2 to 5% by volume of water is admixed and then the emulsion is separated by means of a separator into an oil and a mucilage phase. The separation of the water phase from a water-in-oil emulsion is carried out by centrifugal processes from the prior art (separator, decanter, centrifuge). It is known that the energy expenditure for the separation of the water phase correlates with the amount of added water which is bound in the emulsion. It is therefore the aim of the methods known from the prior art to use only the minimum amount of water necessary.
When using basic solutions for degumming of lipid phases usually much more stable emulsions arise than is the case when an acidic solution is used. Methods are known in the prior art in which emulsions are produced by mixing a basic solution into an oil to be purified; these are then separated again by centrifugation to give a generally turbid oil and aqueous-emulsified mucilage phase. Since the types of mucilages that are present in an oil exist in variable quantities and in varying proportions to each other, it is not possible to calculate the amount of basic compounds and/or a required amount of water that is necessary for separation of hydratable mucilages (gums) from the lipid phases. From the prior art, no methods are known which are universally applicable to different lipid phases and lead to a consistently good separation efficiency of the accompanying substances in oil. The object of the invention is therefore to provide a method with which to reliably and consistently separate accompanying substances, which are present in variable proportions in oils, for further utilization.
It is known from the prior art that alkali solutions lead to saponification of free fatty acids and hydration of phospholipids (see WO 2000/68347, WO2012/173281A1, EP0473985A2). If more than three percent by volume of an alkaline solution is added to an oil containing hydratable accompanying substances and mixed with it, an emulsion is formed which does not spontaneously separate. The document WO2015/185675A1 (process for obtaining glycoglycerolipids and glycosphingolipids from lipoid phases) describes a process in which basic aqueous solutions containing silicates, carbonates or borates in a volume ratio of 0.1 to 3% by volume of vegetable oils or animal fats are admixed, resulting in the formation of a complex with the glycolipids present herein, which can then be separated by centrifugal separation techniques. At larger water volume ratios, the heavy phases obtained after phase separation with a separator were cream-like emulsions containing relevant amounts of neutral lipids.
The patent WO2015/1811341A1 (method for refining lipid phases and use) describes a method in which an aqueous solution containing an amidine and/or guanidine group-containing compound, are admixed to oils or fats, which are subsequently separated by means of centrifugal separation methods together with herein dissolved compounds (free fatty acids, phospholipids, glycolipids, etc.). In this case, an intensive admixture of the aqueous solution showed a significantly improved effect in terms of the depletion of odorants, flavors and colorants, than addition of the aqueous solutions that were only admixed by stirring. It could be documented that, despite the same volume of water which was added and the same concentration of amidine and/or guanidine group-containing compounds in the aqueous solutions, it resulted in a different separation efficiency of odorants and dyes (colorants) through the use of an intensive admixture or a stirring mixing procedure. The volume fractions (volumes) of aqueous solutions required for efficient removal of odorants and dyes were between 2 and 3% by volume. Separation of the water phase was possible only by centrifugal processes. The mucilages were separated in an emulsified form.
EP 0269277 A2 describes a process for the removal of phospholipids or mucilages from triglyceride oils. Therefore, an organic acid or acid anhydride is dispersed in the oil at a temperature not greater than about 40° C. Subsequently, water is dispersed in the oil and the sewage sludge containing mucilage (gums) is removed from the oil to obtain an oil with a reduced content of phosphorus containing compounds. To obtain a refined oil, a further bleaching step is carried out. Bleaching earth (fuller's earth) can be used for this purpose. As organic acids citric acid, maleic anhydride, maleic acid, lactic acid, oxalic acid and acetic anhydride are mentioned, wherein 50% by weight of the aqueous organic acid solution is preferred. The listed amount of added organic acid is between 0.1 to 1.0% by weight. In this case, the addition of water with a content of 0.1 to 3% by weight is disclosed. As a result of the addition of the water and the organic acid or acid anhydride, the phospholipids precipitate in the form of an aqueous sewage sludge. A phase separation to form a water phase is not described. It is clear to a person skilled in the art that the formation of a sewage sludge leads to a significant inclusion of the oil to be purified in the water phase, and thus a high oil loss is associated with the aforementioned method. As a result of the forming sewage sludge and the high proportion of oil in the aqueous phase, this method has the further disadvantage that the phase separation is difficult to accomplish.
DE 1058184B describes a process for degumming vegetable oils, e.g., of soybean, cottonseed, perilla, linseed, peanut, corn and fuel oil by means of water and at least one of the following acid anhydrides acetic, propionic, butyric, maleic, succinic, monomethylsuccinic or dimethylsuccinic anhydride. The acid anhydride and the water may be added to the oil separately or added at the same time. At least 1.5% by weight of water, based on oil, is added. However, it is recommended to limit the amount of water to a minimum, since increased water volumes increase the oil losses and reduce the required contact time especially at temperatures below 60° C. Furthermore, an amount of water of at least 1.5% by weight is described only in connection with a separate addition of acid and water. The examples described contain only examples with at most 3% by weight of water, based on the oil, whereby the oil is first mixed with an acid anhydride and then at most 3% by weight of water is added. After the acid-water treatment, the oil is centrifuged to separate the aqueous mucilage (gum) phase from the oil. It is clear to a person skilled in the art that a sewage sludge results from this, which leads to a significant inclusion of the oil to be purified in the water phase and thus a high oil loss is associated with the aforementioned method. As a result of the sewage sludge formation and the high proportion of oil in the aqueous phase, this method has the further disadvantage that the phase separation is difficult to accomplish.
AT 356 229 B describes a process for degumming triglyceride oils using an acid and water to remove an aqueous sludge containing the accompanying substances after the oil, the degumming agent and the water have been kept in contact with each other for least 5 min. The degumming agents are inorganic or organic acids such as phosphoric acid, acetic acid, citric acid, tartaric acid, succinic acid, etc. or mixtures thereof. First, 0.001 to 0.5% by weight of an acid having a pH of at least 0.5 in a 1 molar solution or its anhydride is dispersed in the oil, then 0.2 to 5 wt. % water is added in the dispersed mixture and finally the aqueous slurry is separated, whereby the mixture of oil, water and acid is maintained at a temperature below 40° C. before the aqueous slurry is separated. Preferably, the aqueous slurry is separated by centrifugation. The oil can be further treated, for example, by bleaching and deodorization process. However, during the acid treatment process, significant amounts of the oil are transferred to the aqueous phase, resulting in a large loss of the oil to be purified. As a result of the sewage sludge formation and the high proportion of oil in the aqueous phase, this method has the further disadvantage that the phase separation is difficult to accomplish.
So far, there is no method in which it is possible to hydrate mucilages, which are present in a lipid phase in an anhydrous form, in such a way that they are extractable by sedimentation from the lipid phase. Furthermore, in the prior art, no aqueous process is known by which only small amounts of the lipid to be purified are being lost during the aqueous treatment of a lipid phase containing mucilages of different origin and composition and with constant effectiveness.
It is therefore an objective of the present invention to provide an aqueous process for the simple and inexpensive purification of a lipid phase and/or for the separation of a mucilage and its recovery from a lipid phase. This objective is achieved by the technical teaching of the independent claims. Further advantageous embodiments of the invention will become apparent from the dependent claims, the description, the figures and the examples.